This invention is directed generally to couplers which permit a remote antenna to be coupled to a radio which has a self contained antenna. This invention is more specifically directed to a coupler which simultaneously disables an internal antenna while efficiently coupling the radio to an external antenna without mechanical switches.
Portable two-way radios and pagers normally have an attached antenna which may be an external monopole or an antenna disposed within the housing of the radio, i.e., a so-called hidden antenna. It may be desirable to increase the effective range of such a radio by connecting it to an external antenna. For example, it is generally known that it is more difficult to communicate with a portable radio or pager which is located in a building having a substantial metal structure or in a vehicle. An external antenna located outside the building or vehicle would greatly improve the communication range of such a radio.
The conventional means for connecting an external antenna to a radio is by a jack or coaxial connector mounted to the radio. Problems associated with direct metal to metal mechanical contacts which carry R.F. current are well-known.
A hidden internal antenna has certain advantages as compared with an external antenna. An internal antenna makes the radio less awkward to use and the possibility of damage to an external antenna is eliminated. Such an internal antenna is disclosed in U.S. Pat. No. 4,571,595 entitled DUAL BAND TRANSCEIVER ANTENNA. Although internal antennas have certain advantages, the range of a radio utilizing an internal antenna is typically less than that for a comparable radio utilizing an external antenna which is often substantially larger. Therefore it is desirable, especially with respect to internal antennas, to have the capability of extending the range of the radio by means of a remotely mounted antenna
Where a remote antenna is to be coupled to a radio, some means is normally provided to disengage the attached or internal antenna when the remote antenna is in use. A conventional means for disabling an internal antenna is to utilize a mechanical jack or associated switch to disengage the attached antenna circuit when the remote antenna connector is inserted into the jack. Such mechanical assemblies suffer from problems associated with direct metal to metal connections especially where RF energy is being transferred.